Is Class 1 fire rating the same as 1 hour fire resistance rating?

In short, No - in the UK "Class 1" is a form of performance that indicates how easily something burns ('Class 4" being the worst).

Fire resistance on the other hand is a term that relates to a construction's ability to resist the passage of fire (e.g. a wall, floor, door etc).

The fact that a material is "Class 1" doesn't necessarily have any bearing on its fire resistance performance. For example, PVC cladding can be obtained to a 'Class 1' rating, but it wouldn't contribute much to the wall's fire resistance performance at all.